A light-emitting element having a light-emitting layer has been used for a display recently. Such a display using a light-emitting element has advantageous effects such as a wide viewing angle, a high-response speed and low power consumption, as compared with a display having a liquid-crystal layer, and thus, has been developed actively.
Light-emitting elements have a problem that their light-extraction efficiency is low due to scattered light or reflected light inside the light-emitting elements. The light-extraction efficiency needs to be enhanced.
In order to enhance the light-extraction efficiency, there is proposed a structure in which a transparent electrode used for an electrode of a light-emitting element has a different thickness according to emission colors (Reference 1: Japanese Patent Laid-Open No. 2003-142277).